This isolated outpost was once the only place to cross the Colorado River for hundreds of miles.

Most-visited and most-photographed slot canyon in the American Southwest.

Eons ago, a rushing lava river formed this pristine passage through solid rock.

The Slovenian architect designed many landmarks in the capital city, including his own dream house.

Martin Bricelj Baraga's monolithic sculpture measures the blueness of the sky, and changes color to match it.

When a supermarket opened up shop within a medieval building it became protected by UNESCO on a technicality.

This stunning, out-of-the-way Croatian monument commemorates a community's uprising against occupying fascist forces.

The oldest church in the Estonian capital is home to over 100 fantastical cemetery coats-of-arms.

This only museum in the world dedicated solely to mushrooms.

Longest fortress system anywhere in Europe.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

A musical instrument played by the sea.

Now harmless, this looming post struck fear into the heart of medieval troublemakers.

A World War II evacuation tunnel turned into a history display of Croatian state and people.

This one-time health resort was used by aristocrats around the world.

This unique structure allowed boats to bypass underwater mine barriers in the channel to enter the harbor.

A full figure 4th century incorruptible saint lies in a glass coffin in Croatia.

Gargoyle head that brings good luck.

A subterranean house of worship carved right out of the bedrock.

A vibrant portrait celebrates the actress in her hometown.

The artwork immortalizes one of 20th-century Ireland's leading creatives.

A 90-acre park on former landfill that hosts an annual kite festival.

This collection of over 50 murals celebrates Brussels' rich history as the self-proclaimed home of the "comic strip."

This religious complex carved into a cliff is steeped in legends of miraculous stags and the Holy Grail.